On OSX Lion (didn't try older versions) the driver does not properly release the mbed for use in VMWare fusion.

That's unfortunate.

I haven't tried using the mbed from VMWare. I just tend to use OSX itself for most of my mbed development. Is there a tool that you need to run on Windows for your mbed development that stops you from running everything natively under OSX? On OS X, the web based compiler obviously works and I find the virtual serial port easier to use as it doesn't require a special driver.

I do all of my development on OSX without any problems, but we have a Windows license of LabView that I need to have the mbed communicate with. The mbed will eventually be running on a machine that I don't regularly have access to (it's deployed at a remote location) so I need to debug in my office. On the remote machine LabView was throwing a "Serial Port Error" after sending a start command to the mbed (which worked fine, the mbed started data collection as expected). For now I'll work around this, but it would be handy to see this driver issue fixed in a future release.

Uninstalling and reinstalling VMWare resolved the issue. Apparently this happened with other Serial adapters and USB memory devices as well.